 Is there any way to get this result?

I did a test in a job interview and one of the questions was something
like
make an algorithm that prints the sum of the first 4 million even
numbers
of fibonacci sequence.

in the test I wrote pseudo code, but now I’m trying to test my logic
with ruby:

num1 = 1
num2 = 1
next_number = 0
total = 0

1.upto(4_000_000) do
next_number = num1 + num2
num1 = num2
num2 = next_number
total += num2 if((num2 % 2) == 0)
end

puts total

is there any way to have the total value?
is this a good code or there is a clever way to write it?

On Wed, Nov 6, 2013 at 5:24 PM, Rafael M. [email protected] wrote:

num2 = 1
puts total

is there any way to have the total value?
is this a good code or there is a clever way to write it?

I think the code is OK - except your looping condition. It does not
match the problem description.

Kind regards

robert

I don’t have a working copy of ruby on me, but I feel like a more
Rubyish
way of implementing it would be the following. The hacky bit with the
hash
is to get a memoized collection of Fibonacci numbers (source:
pretty awesome mind blown feeling when I saw that answer the first time.

n = 4,000,000
fib = Hash.new{ |h,k| h[k] = k <= 1 ? k : h[k-1] + h[k-2] }
fib.values_at(*(0…n).step(2)).inject(:+)

On Wed, Nov 6, 2013 at 11:17 AM, Robert K.

Oh bah, I did it for every other value of the fib sequence instead of
the
even values. Take out the step and do a more complex inject.

Robert K. wrote in post #1126613:

On Wed, Nov 6, 2013 at 5:24 PM, Rafael M. [email protected] wrote:

num2 = 1
puts total

is there any way to have the total value?
is this a good code or there is a clever way to write it?

I think the code is OK - except your looping condition. It does not
match the problem description.

Kind regards

robert

the problem was really to loop through 4 million numbers of fibonacci
and if the current number was even you should add to the total,
the interviewer checked my pseudo code and found it correct

thanks for the replies

(2…n).step(3) should get you all the even fib values.

I would prefer to use

total += num2 if num2.even?

when I am testing for even-ness of a number.

Hope this helps,

Mike

On Nov 6, 2013, at 11:24 AM, Rafael M. [email protected] wrote:

num2 = 1
puts total

is there any way to have the total value?
is this a good code or there is a clever way to write it?

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